An architect noted for his restoration of castles, and his promotion Arts and Crafts style in Scotland. Lorimer was born in Edinburgh, the son of James Lorimer (1818-90), a Professor of Law, and educated at the Academy and University in the city. He started his career working for Sir Robert Rowand Anderson (1834 - 1921). He began his own practice in 1892 and went on to build or remodel a large number of country houses, castles and several important public buildings. He was the architect of the Scottish War Memorial at Edinburgh Castle and the Thistle Chapel at St. Giles (Edinburgh).
He lived in Kellie Castle (East Fife), continuing the restoration begun by his father. His elder brother was the artist John Henry Lorimer (1856 - 1936) and his son, Hew (1907-93), became a noted sculptor.